There is conventionally provided a road illumination system for illuminating a road (see, e.g., Paragraph [0042] and FIG. 1 of Japanese Patent Application Publication No. 2002-305088 (JP2002-305088A)). The road illumination system includes a plurality of illumination apparatuses installed along a road to light up the road, a service marker provided in a position through which a motor vehicle moving toward an illumination target region on the road can pass and a wireless tag for receiving a signal wirelessly sent from the motor vehicle passing over the service marker.
In the road illumination system, the respective illumination apparatuses are dimmed or turned off until the wireless tag receives a signal from the motor vehicle. If the wireless tag receives a signal from the motor vehicle, the respective illumination apparatuses are turned on at a specified illuminance for a specified time. With this road illumination system, it is possible to enhance safety by turning on the respective illumination apparatuses at a specified illuminance when a motor vehicle passes through. It is also possible to save energy by dimming or turning off the respective illumination apparatuses when a motor vehicle does not pass through.
The road illumination system disclosed in JP2002-305088A is capable of saving energy while enhancing safety. It is however necessary to employ a large-scale control device for controlling the illumination apparatuses. Also necessary are wiring lines for interconnecting the control device and the respective illumination apparatuses. Therefore, the cost of the illumination system as a whole grows higher.